Abstract: Sample introduction apparatus useful in liquid chromatography and including a valve body having at least one fluid passage of precisely defined volume to receive a sample material and having another fluid passage delivering carrier liquid to a liquid chromatograph. The valve body can be manipulated to place the precisely defined volume in the chromatograph fluid circuit, so that the sample contained within the volume is positively displaced into the chromatograph.

Abstract: Apparatus used in the field of liquid chromatography. There is disclosed pump apparatus for continuously delivering a flow of carrier liquid either at a constant rate of flow or at a constant pressure. The pump apparatus includes a pair of differential-piston pressure intensifiers which are sequentially operated so that the high-pressure sides of the pressure intensifiers sequentially supply carrier liquid to the chromatograph column. Each pressure intensifier is sequentially operated by a constant-rate of flow application of hydraulic liquid, with essentially pulseless operating transition between pressure intensifiers occurring during constant-pressure application of hydraulic liquid to both of the pressure intensifiers at a pressure measured during previous constant-volume hydraulic operation. An embodiment of the pump apparatus pumps plural carrier liquids in desired fixed or variable proportions.